The present invention generally relates to seals for fluid or gaseous media and is more particularly directed to sealing between a static and a dynamic surface in which the dynamic surface engages and disengages the seal while the seal is pressure energized.
Typical seal applications in which a transient surface is sealed includes ball valves, butterfly valves, plug valves, pistons, quick connect couplings and so forth. In such applications, it is difficult to prevent a seal from deforming and/or blowing out due to the rapid change of pressure across the seal. In these applications, there is a need to resist blow-out of the seal which can occur during the time when a piston or other surface moves away from the seal temporarily while residual pressure is still higher in the seal cavity. This can cause a seal to blowout or deformation.
Prior art seal designs used for such conditions have included captivated elastomeric o-rings and seals requiring specialized mounting glands configured to retain both front and rear edges of the seal. In addition, housing of such prior art seals requires a plurality of vent holes in the gland to allow the energizing media to enter and exit the seal cavity. Such seal glands have been large and complex and for most applications are not amenable for retrofitting in existing products.
The present invention is directed to a self-contained seal design with support features to prevent the seal from deforming and/or blowing out under rapid pressure changes due to repeated engagement and disengagement from dynamic sealing surfaces.
A self-contained anti-blowout seal in accordance with the present invention generally includes a seal jacket having a static seal surface and a dynamic seal lip with a cavity therebetween. The cavity is open to one side of the seal jacket and a retaining ring is provided and disposed, in part, within the cavity and proximate the static seal surface for pressing the static seal surface against a mounting surface.
The retaining ring includes a surface extending outside of the cavity for bearing against the mounting surface and a depending portion extending over the cavity opening. Vent holes in the depending portion provide communication with the cavity for enabling a sealing media to enter and exit the cavity as a seal is pressure energized. A biasing element is disposed in the cavity for forcing the dynamic seal lip against a moving member. This configuration provides for a seal that can experience rapid decompression as the moving member disengages the dynamic seal lip without blowing out or otherwise self-destructing due to residual pressure in the seal.
The seal can be oriented to provide dynamic sealing on an inside diameter, an outside diameter, either as a face seal or at an angle, for example, on a ball valve or partially engaging a surface such as may be used in a butterfly valve. All of these embodiments will be hereinafter described.
More particularly, the retaining ring depending member may include a ledge extending therefrom for engaging the dynamic seal lip for preventing such seal lip blow-out during disengagement of a moving, or sealing, member.
Still more particularly, a snap-in back-up ring may be provided and disposed between a heel portion of the seal jacket and a moving member for preventing the seal lip from bending past the ledge.
A number of biasing elements may be utilized including a canted coil spring, an elastomer o-ring, a spiral strip spring, a leaf spring or a garter spring.
In another embodiment of the present invention, the retaining ring may further comprise a biasing surface for preventing longitudinal movement of the seal and a back-up ring may further comprise a body portion extending outside of the seal jacket for holding the static seal surface against the mounting surface.